A computer system is comprised of many hardware and software components that work together to perform tasks requested of it by a computer user. Many of these components are never seen by a user, and most users don't know or care what function they perform. The computer display, however, is probably the most visible component of the computer system, as it is the usual interface between user and machine.
Although computer users may be tolerant of substandard performance in the computer components they don't see, they are far less tolerant of substandard performance in components they do see, such as the computer display. For example, when computer users work with a word processing program, they want to be able to enter text as quickly as they can type without having to wait for the display to catch up with them. Likewise, when they press a key on the keyboard, such as "enter", "page up" or "page down", they want the display to respond quickly and efficiently so they do not have to wait. If they have to wait for the computer display to perform a seemingly simple task, like scrolling to the next page, they can become frustrated, and often take out their frustration by punching the keyboard (which can damage the keyboard) or punching the screen (which can damage the hand).
Although this problem exists in standalone "smart" displays, such as personal computers, this problem is exasperated if the computer display is a fixed function display connected to a workstation controller. Fixed function displays are often called "dumb" displays, since these displays merely display the data that is sent to them by the workstation controller, and have little if any smarts of their own. For example, every time the user of a fixed function terminal wants to scroll to a new page, the workstation controller must transmit the new page of data to the display. Since the workstation controller often controls several fixed function displays that are making simultaneous requests for new data, a particular computer user may have to wait for the workstation controller to service his fixed function display. This delay can be quite perceivable and annoying if the workstation controller is busy. Delays are also caused in transmission between the workstation controller and the display especially if the workstation controller is a long distance away from the display, or is remotely attached via telephone lines.